An interlock is an alcohol-measuring device with a vehicle immobilizer in a motor vehicle. According to the current state of the art, the alcohol measurement is carried out as a breath alcohol measurement. However, this is not a necessary condition for an interlock system, but other breath alcohol measurements may also be used, in principle, for the system being described here. The goal of an interlock is to prevent a driver who is under the influence of alcohol from starting the vehicle engine. The interlock device can be installed in the motor vehicle in a simple manner. By installing an interlock, accidents related to alcohol can be prevented from occurring. Furthermore, it is suitable for supporting long-term behavioral changes in handling alcohol. Interlock devices are often installed in vehicles later. This is done either for a certain time period or for the remaining service live of the vehicle.
The practical procedure is, in general, such that the driver of the vehicle is prompted by the interlock to perform a breath alcohol measurement when he is attempting to start the vehicle. Depending on the result of this measurement, the signal chain for starting the engine is then released and the driver of the vehicle is enabled to start the engine. To improve the tamperproofness of the interlock concept, it is, furthermore, common practice that the driver of a vehicle equipped with an interlock system has to give another breath sample after some time. It is ensured by this, for example, that the first sample was not given by another person.
A device for the repeated giving of a breath sample is known from EP 1 874 580 B1.
To perform a repeated test, the driver is prompted after a time tW to give another breath sample. This shall ensure that the person who gave the first sample is also the driver of the vehicle and that no alcohol was consumed during travel. This time tW is determined such that it is a time interval after the last test within which the time tW is calculated according to the random principle. An active alcohol test and a passive alcohol test are used for this. A passive test is an alcohol test during which the driver of the vehicle does not blow directly into the device, i.e., he does not perform an active test, but the device automatically takes a gas sample. However, it happens in practice that repeated tests are performed, in general, during travel, i.e., the vehicle is not stopped.
Giving a breath sample into an interlock breath alcohol-measuring device means that it is absolutely necessary to blow into the mouthpiece of a hand-held device, i.e., to bring this hand-held device to the mouth with at least one hand in order to then give this sample. Furthermore, it is common to display the result of the measurement as, e.g., “Bestanden”/“Nicht Bestanden” or “Pass”/“Fail” on the display of the hand-held device. If the criteria for an acceptable breath sample are not met, i.e., blowing time too short, blowing too weak or incorrect use of a breathing technique, blowing and sucking, and blowing with a humming noise, this is usually also displayed on the display and a repeated breath sample is requested. The display must also be watched for this, and driver of the vehicle would thus be distracted from the traffic proper.
There are often limitations for similar actions in the vehicle. Thus, there often are provisions in the laws that prohibit, in principle, the use of a telephone for the vehicle driver while driving unless at least a so-called hands-free unit is used. Such a device enables the vehicle driver to use his telephone without holding the cell phone at the ear with at least one hand.
Recognition of the state of motion of a vehicle is known from DE 102 51 281 B3. This document shows a process for recognizing the motion of a motor vehicle, in which an unacceptable bypassing of blocking, e.g., by pushing, is detected by means of an acceleration sensor.